Two World's War
by meerjax
Summary: Its 1939, and Germany is invading Poland. But behind the mundane war, Hitler's shadow army grows stronger, thousands of demons at his command, taking the institutes, coming for Idris. Rivvy Lightwood doesn't care about the war- she just wants her brother back. But as she gets closer, she becomes entangled with her fate, and with the boy she can't help but fall in love with.
1. Chapter 1

They came at midnight.

What started out a low rumble from beyond the horizon soon turned to screams and explosions and flashing lights. Mundane men in military uniforms pored into the city, marching down the streets in perfect formation and as the local people scattered in all directions, some hauling sacks of food and belongings, some clinging onto their children and crying out for mercy. No one knew where they came from, but what they wanted was clear enough. They wanted the city. They wanted Warsaw.

"We have to do something." Rivvy said again, gazing across the dark library from her perch at the high, stained-glass window. Her grandfather stood with his back to her, leaning against a broad oak desk with his shoulders hunched. Even in his old age he was an imposing man, broad and tall with a thick mane of silver hair and beard bushy enough to conceal most of his tan, weather-worn face.

"You know we can't." Steven, Rivvy's tutor and her grandfather's advisor, replied softly from another dark corner of the library. They'd blow out all the candles and gas lamps when the first of the mundane troops reached the city. There was no way for them to even see, let alone enter the institute, Rivvy knew- but an invasion of this scale, even a mundane one, had put her grandfather on edge enough to call the entire conclave to institute to hole up and weather the attack.

"But we're shadowhunters." Rivvy said angrily, her voice rising above the hush in the library enough to make her grandfather wince, she noticed with satisfaction. "Helping mundanes is what we _do_."

Steven took a slight step forward so that the silvery light from the window fell across his face, the occasional flash of gunfire or explosion from the streets below lighting him up enough for Rivvy to see he was wringing his hands. Curious.

"We do not interfere with mundane politics and affairs." He said calmly, his slow, easy tone not matching the tension in his body. His lips were pressed into thin line, the wrinkles in his forehead deepening as he furrowed his brows in a way that left Rivvy wondering if maybe- just _maybe_ \- she might get to him yet.

"So we sit back and let them kill each other?" She demanded, eyes flickering to her grandfather, who hadn't moved to turn around in what seemed like hours.

Steven sighed and ran a hand through his hair, dark and streaked with grey. "Until they threaten the nephilim or any downworlders, yes. We leave them to fight their own wars, as we always have."

Rivvy shot the back of her grandfather's head a look of pure steel. "Fine." She spat, fingernails biting into her palms as she pushed herself off the windowsill. "We'll just hide in here while innocent people die."

As if the invisible chord holding him back had snapped, her grandfather whorled, his dark blue Lightwood eyes flashing with a burst of anger. Anger, Rivvy realised, that was directed at her.

Her grandfather had never hit Rivvy or her brother since they came to live with him in Warsaw at the beginning of the summer, not like other guardians often did, but she had been at the receiving end of his rage more than a few times, and she knew it was only a matter of time before he resorted to other forms of discipline. As he straightened to reach his full, imposing height, Rivvy saw him not as the quiet grandfather who had taken her in after her mother's death, but as the well respected head of the Warsaw institute. Suddenly, she understood why the conclave seemed to tip toe around him so carefully.

He opened his mouth to speak, shout, _something_ , and there was thunder in his eyes, but just as Rivvy was shrinking away the library doors clanged open and three shadowhunters charged in. One of them Rivvy knew by name- Henry Cartwell was an emissary from the clave who had arrived a few weeks ago, but the other two members of the conclave rarely visited the institute, and Rivvy had never spoken to them.

Henry was the first to reach her grandfather, where he bent with his hand on his knees, panting as if he'd run all the way from the suburbs.

"What is it, Cartwell?" Rivvy's grandfather demanded, all traces of his annoyance towards Rivvy replaced with a cool, profession tone of authority. "Out with it, man."

"The mundane army." Henry panted, and when he straightened, his face was twisted into an expression of shock and fear. "There's more coming, behind them, from the Southeast."

"You know very well there is nothing we can do under clave law, Cartwell." Her grandfather grumbled, some of his straight posture giving way to a slight hunch of defeat. "The mundanes can either fend for themselves, or-"

"Not mundanes." Henry said cooly, an edge to his voice that sent a sudden chill through Rivvy, still watching from the safety if the window. "Demons."

The room went cold, as if all the heat from the fire had been leeched out by the very mention of the word, as if everyone simultaneously sucked in their breath and held it. The silence was palpable, collecting in the air and sticking to Rivvy's skin like moisture on a humid day, making her tongue thick and her head fuzzy.

"Demons?" Her grandfather repeated after what seemed like an age.

Henry Cartwell nodded, and the two members of the conclave behind him stepped forward, witnesses to his testament.

"An army of them."

The front hall of the institute was a sea of noise and tension. The entire conclave was gathered below the first floor landing, almost all dressed in gear, huddled in groups to speak in hushed voices, as if whispering about the oncoming threat was enough to put it off. There was no fear in their voices, but when they looked up to Rivvy's grandfather as he stood on the balcony, as they gazed up at the head of their conclave, there was no joy, no warmth. None of the excitement and adrenaline Rivvy usually associated with a hunt.

No, in the faces that all turned towards her grandfather, there was nothing but steely resolve and apprehension, and this alone was enough to turn Rivvy's blood to ice.

"We've sent out scouts." Henry Cartwell was saying hurriedly, hovering like a fly at her grandfather's elbow. "To see how many. They haven't returned."

"We'll take no chances." Her grandfather said, ignoring Henry completely and raising his voice so the entire conclave could hear, even from below the balcony. "Ready yourselves for battle. We won't make a move until we know what we're up against." There was a murmur of agreement, the distinct sound of people checking weapons. "River," Rivvy's grandfather turned to her, his voice becoming quiet. "Wake your brother and bring him to the library. Both of you need to portal to Idris tonight."

"What?" Rivvy gaped at him. "No! Send James, but I'm staying."

"It's too dangerous." Her grandfather replied, dismissively. "You'll get in the way."

"I'm _sixteen_ , grandfather!" Rivvy cried, not caring now about angering him. She glanced to Steven for support- _he_ knew what she could do. He'd seen her train, he _knew_. "I've been hunting for years, I can handle myself."

"You're inexperienced, and we don't know what we're facing." It was Steven that replied this time, calm as ever. Rivvy just stared at him, the betrayal rendering her speechless. What were they _thinking_? If it really was an army, they needed all the shadowhunters they had, and that meant her. Wasn't this what they'd trained her for?

"But-"

"Go and get your brother." Her grandfather said, and the authoritative tone was back, marking the end of discussion. Rivvy simply gave him a look of pure venom, resisting the urge to hiss. Even she knew how ridiculous she must look to Henry Cartwell and the other two shadowhunters- she was small for sixteen, and still in the floral, butterfly-sleeved dress and hat she'd dressed in that morning. To them, she may as well be a little mundane girl, weak and frilly. She scowled one last time at them all before turning on her heel and stalking for the stairs. Let them think that, she thought sourly, just let them wait and see.


	2. Chapter 2

"Rivvy?"

A voice in the dark, the soft sigh of sheets being pushed back. Rivvy padded silently to the bed, knowing the room so well she didn't need a light. When she reached the fourposter bed in the centre she found her brother sitting up, swinging his legs over the side, his feet not touching the ground.

"It's me." She said softly, perching herself beside him and wrapping her arm around his narrow shoulders, pulling him into her in a sort of half-hug.

"Have the armies stopped yet?" Her brother asked, his voice quiet, sweet. Innocent. He was innocent, too young to have ever fought a demon, to have tracked a rogue werewolf or a vampire clan, to have witnessed the brutality of the world. Rivvy's eyes were adjusting to the darkness now, and she could just make out the outline of his small, childish face, his hair overgrown and brushing into his eyes, sticking up on one side from where he'd slept on it.

She sighed. He was only eight years old, he was too young to be caught in all of this, all the fear. But Rivvy remembered when she was that young. She remembered being sent from the room when anyone came to the house with news, spending hours perched at the top of the landing in their town house in Idris, trying to hear what they said, to learn, to understand. But they never let her hear, and she always resented them for it. Her brother was young, but he was a shadowhunter.

She signed heavily. "No, they haven't." She said, tucking a long strong of hair behind her ear. "And I don't think they'll leave anytime soon, either."

James nodded in the darkness, as if he'd already guessed. "What do they want?"

"I don't know," She admitted. "But it's not for us to worry about. They're mundanes, we're shadowhunters. The conclave will handle it." She hated the words as much as the first time she'd heard them from her grandfather's mouth.

"But grandfather said we didn't need to-"

"We're going to go back to Idris for a while." Rivvy cut it, hating the clip in her voice. "Just you and me. For a…" She paused, and then, "For a holiday." She inwardly cursed herself for the lie- but what could she say that wouldn't scare him half to death?

Avoiding any more of his curious questions, she gently pushed herself off the bed and felt for the witchlight lamp on the side table. At her touch it flickered to life, bathing the room a light so bright she had to close her eyes until they adjusted. Her brother's room was strewn with clothes and books and toys, but it didn't take her long to cross to the large, dark wood armoire and find a duffle bag large enough to hold her clothes and his.

"Get your things." She instructed, scooping up an armful of her own clothes from the armoire- most of her things were in her brother's room, just as she spent most of her nights in here, protecting him from the nightmares that hadn't left since their parents had died. "We won't be gone long, you won't need much." _I hope_.

When they'd filled the duffle bag with random items of clothing and some of James's toys and books, Rivvy slung in over one shoulder and took her brother's hand, giving him a thin, forced smile, hoping he couldn't see the fear in her eyes.

The empty corridors of the institute seemed to leer at her as she walked, clinging to her younger brother, mocking her for her fear, for running when her city was under threat.

 _An army of demons_.

The words seemed to ring around inside her head, somehow hollow and meaningless, like it wasn't really happening. Could the scouts have simply seen a line of shadows on the horizon and mistaken them for something else, made jumpy by the siege that was happening around them? Even as she thought it, she knew it wasn't true. Shadowhunters didn't make that kind of mistake.

She winced as she caught sight of herself in a floor-to-ceiling mirror at the top of the stairs, looking for all the world like any average mundane girl; small, thin, her dark curls left unbound to catch in the ruffles of her dress, her skin still tanned from summers in Idris, almost hiding the scars left by the burning of runes on her skin. A little girl, running in the face of danger. Not a warrior, not even deserving of the name nephilim.

Her thoughts were cut short as they reached the landing above the main hall, and Rivvy stopped in her tracks, James at her side.

The air in the room was electric, not like the uneasy shuffling of before, but as if someone had frozen time and everyone there with it. It was far from quiet- voices rang out over the entire space, too muddled together for Rivvy to make out any words, but something about the way they were loading themselves with weapons, the way they stood, as if the battle had already begun, sent a cold trickle down her spine.

Spying her grandfather in the midst of the conclave below the balcony, Rivvy turned to her brother and let go of his hand.

"Stay here until I come back up, okay?" His dark eyes, almost identical to her own, looked up at her with a look of utter, unfaltering trust. James put on a brave face and gave her a nod, and she tousled his hair as she stepped past him to jog down the stairs, throwing herself into the throng at the bottom. Most of the shadowhunters paid her no heed, and she was grateful for the natural nimbleness which came with her small body as she slipped and ducked her way towards her grandfather. Although he still wore the fine black clothes and polished shoes, he'd strapped a broadsword across his back, the handle sticking up above his left shoulder like a second, watchful head.

As she approached him she braced herself to tug on his sleeve, tap him, pester him until he deigned to pay her any attention- but to her surprise his eyes found hers almost as soon as she reached him.

"River," he said, grasping her upper arm in a grip like iron and dragging her to the edge of the room. "We're evacuating everyone." She blinked, the tight fear in his voice sounding warning bells in her head. She had never seen him so tense, never seen him as anything other than a pillar of stone, unmovable and fearsome.

"What's happened?" She demanded.

He shook his head. "No time, they're coming faster than we thought. Get James, you'll be the first to portal to London."

 _London?_

Before she could open her mouth to argue, a screeching so loud she could have sworn she felt it cleave her skull in two filled the hall- filled the entire _building_. The windows above the tall front doors shattered, shards of stained glass scattering as they showered down on the shadowhunters ducking and covering their ears. For a moment, Rivvy could think of nothing but that noise, earthly, piercing, so loud it drowned out the screams of the men and women around her, drowned out everything save for the rush of blood in her ears. But then a stream of black, winged creatures soared in through the smashed windows, and it was as if a wire had been cut, freeing them all from the spell of the noise.

Demons swooped down on the shadowhunters, hoards of them, each one bigger than a man, black and scaled with a set of bat-like, leathery wings. Weapons were drawn, light blazing up as seraph blades flashed all around them, but all Rivvy could think of was how utterly useless she was in that stupid frilly dress, without even a dagger to defend herself, to defend-

 _James_.

She spun around, ducking as someone- Steven, she realised- roared past her in a flurry of battle-anger, his twin blades flying as he sliced through the flesh of a winged demon coming straight for her. She didn't have time to thank him as she hurtled forwards towards the stairs, where James was cowering on the balcony, alone and undefended. All around her the shrieks of the demons mingled with the cries of the nephilim, and the floor was slick with blood and black ichor, the stench of it like acid in her nose.

She was almost at the stairs when one of the winged beasts crashed into the railing in front of her, uncoordinated in such a confined space, but as it turned to her she swore she saw a flicker of amusement in its beady eyes. Rivvy's blood was boiling, with adrenaline, with anger, with her need to protect her own. She hissed at it, ready to leap, tear at its flesh with her fingernails, bite through its skin if she had to-

When a set of thick, very human arms clamped around her middle, pulling her back, back and away from the stairs. Steven growled in her ear as she thrashed against him, her eyes locked on the tiny, fragile shape of her brother up on that landing, crouching against the banister, his eyes huge and fixed on something below him. Rivvy followed his terrified gaze right to the bottom of the stairs, to the creature she'd just been torn away from, the creature which now edged its way upward, claws digging into the wooden bannister, wings slicing at the air as it fixated on James with a predatory gleam in its eyes.

A scream not unlike the demons' shrieks erupted from Rivvy's mouth and she tore at the arms that held her, oblivious to the blood that coated her fingernails as she scratched at her tutor's skin. Behind them, the iridescent glow of a portal flared, and the shouts of someone ushering the conclave through echoed in her ears. Steven was backing up towards the portal as two shadowhunters, a man and a woman, sliced at the demon hoard making an attempt to follow them.

"Stop, _stop!_ " Rivvy cried as the glow from the portal began to encase her, blurring the edges of her vision. The demon on the stairs had almost reached the top, almost reached her brother, who held out a shard of glass in front of him, his face twisted in terror.

"We have to go back, we have to get him!" But Steven just kept backing up, his hold on her getting tighter. " _James!_ " She screamed, trying in vain to twist, to kick, scratch, anything to get Steven's arms to slip just a little-

The demon reached James just as they reached the portal, and Rivvy was utterly powerless as she watched it close its skeletal black arms around her brother's middle and lift him into the air, vanishing out the smashed window and into the night just as Steven stumbled back fully through the portal, pulling Rivvy back into the darkness.


End file.
